Shi-Hai Xu

Isolation, structure determination, and synthesis of galaxamide, a rare cytotoxic cyclic pentapeptide from a marine algae Galaxaura filamentosa.

Galaxamide (1), a rare cyclic pentapeptide, was isolated from the marine algae Galaxaura filamentosa. A preliminary bioassay of Galaxamide showed remarkable in vitro antiproliferative activities against GRC-1 and HepG2 cell lines. The first total synthesis of the cyclic peptide was achieved for further biological evaluation.

New Furan and Cyclopentenone Derivatives from the Sponge-Associated Fungus Hypocrea Koningii PF04

Two new furan derivatives, hypofurans A and B (1 and 2), and three new cyclopentenone derivatives, hypocrenones A–C (3–5), along with seven known compounds (6–12), were isolated from a marine fungus Hypocrea koningii PF04 associated with the sponge Phakellia fusca. Among them, compounds 10 and 11 were obtained for the first time as natural products. The planar structures of compounds 1–5 were elucidated by analysis of their spectroscopic data. Meanwhile, the absolute configuration of 1 was determined as 2R,3R by the comparison of the experimental and calculated electronic circular dichroism (ECD) spectra. All the isolates were evaluated for their antibacterial and antioxidant activity. Compounds 1, 10, and 12 all showed modest antibacterial activity against Staphylococcus aureus ATCC25923 (MIC, 32 μg/mL). In addition, compounds 1, 10 and 11 exhibited moderate DPPH radical scavenging capacity with IC50 values of 27.4, 16.8, and 61.7 µg/mL, respectively.

A new antitumor arabinopyranoside from Laurencia majuscula induces G2/M cell cycle arrest

A new arabinopyranoside was isolated from the alga Laurencia majuscula (Harvey) Lucas, collected from the Xisha Islands in the South China Sea. Its structure was elucidated as hexadecyl‐1‐O‐α‐l‐arabinopyranoside by spectroscopic analysis. It was found that arabinopyranoside had significant antitumor activity in LOVO and Bel‐7402 cell lines. Flow cytometric analysis showed that arabinopyranoside arrested the cell cycle in the G2/M phase. Western blotting demonstrated that the protein expression of CDK1 and cyclin A related to the G2/M phase decreased markedly with arabinopyranoside treatment, with slight changes in cyclin B1 expression. Taken together, the findings identify a potential new antitumor therapeutic arabinopyranoside isolated from red alga Laurencia majuscula. Copyright

Paper Synthesis, Cytotoxicity and Apoptosis Induction in Human Tumor Cells by Galaxamide and Its Analogues

Our previous study reported that galaxamide, which is a cyclo-pentapeptide containing five leucines that was extracted from Galaxaura filamentosa, displayed remarkable anticancer cytotoxicity. This novel cyclo-peptide provided a new skeleton for the structural modifications used in finding new drugs with better anticancer properties. In this study, five analogues were synthesized based on changing the number of d/l amino acids by adding a new amino acid, phenylalanine. Galaxamide and five of its analogues were evaluated through MTT assays to examine their cytotoxic activities. We found that modified analogue 5, which is referred to as A5, displayed broad spectrum cytotoxic activity toward every cell line tested; in addition, the IC50 of A5 was lower than that of galaxamide and the other analogues. Furthermore, we used flow cytometry and western blot assays to investigate whether galaxamide and A5 could induce cancer cell apoptosis. The flow cytometric studies showed that HepG2 cells treated with different concentrations of galaxamide or A5 over 72 h displayed significant and dose-dependent increases in the percentages of early-stage apoptotic cells. Western blotting revealed that both compounds induce caspase-dependent apoptosis in HepG2 cells through a mitochondria-mediated pathway. The results demonstrate that galaxamide and its analogues have potential applications as clinical anticancer drugs.

Secondary Metabolites Isolated from the Sponge-Associated Fungus Nigrospora oryzae

Sponges represent one of the top-ranking sources of marine fungal diversity [1]. Many sponge-associated fungi are capable of producing structurally diverse and highly bioactive secondary metabolites [2]. Moreover, metabolites derived from sponge-associated fungi facilitate the development of sustainable products for the pharmaceutical, nutraceutical, and cosmetic industries [3]. Hence, we have paid ongoing attention to bioactive metabolites from sponge-associated fungi. The fungus Nigrospora oryzae was isolated from the marine sponge Clathrina luteoculcitella collected off Yongxing Island in the South China Sea. Nigrospora oryzae produces plenty of metabolites [4]. However, there is as yet no study on secondary metabolites isolated from the sponge-associated Nigrospora oryzae. The strain was cultured in Czapek–Dox medium at room temperature for 40 days in artificial seawater. The culture broth was extracted three times with EtOAc, and the EtOAc solvent was removed under vacuum to yield a brown gum (3.5 g) from a 10 L culture. The extract was chromatographed on a silica gel chromatographic column and further purified by semipreparative HPLC to afford compounds 1 (2 mg), 2 (4 mg), 3 (3 mg), 4 (3 mg), 5 (6 mg), 6 (7 mg), and 7 (6 mg). These seven compounds were unambiguously identified as 2,4-dichlorobenzoic acid (1) [5], cyclo-(Pro-Val) (2) [6], cyclo-(Pro-Leu) (3) [7], cyclo-(Pro-Ile) (4) [6], cyclo-(Pro-Tyr) (5) [6], cyclo-(Pro-Phe) (6) [8], and cyclo-(Leu-Tyr) (7) [9] by comparing the NMR spectroscopic data with the literature. To the best of our knowledge, both 2,4-dichlorobenzoic acid (1) and diketopiperazines (DKPs) 2–7 were isolated from the genus Nigrospora for the first time. DKPs exhibit diverse and remarkable biological activities, such as antimicrobial, antioxidant, and antitumor effects [10]. In addition, DKPs are utilized by gram-negative bacteria [11] and archaea [12] for communication by activating or antagonizing N-acylhomoserine lactone-mediated quorum sensing systems [11]. Our results showed that the main secondary metabolites produced by the sponge-derived fungus Nigrospora oryzae were diketopiperazines. Indeed, DKPs are widespread in three domains of life, i.e., bacteria, archaea, and eukarya [10–12]. Here, we offer a possible explanation for the extensive distribution of DKPs. As quorum sensing signals for intraspecific communication, DKPs are synthesized at a high transcriptional level in gram-negative bacteria [11] and archaea [12]. Yet, in fungi, DKPs may not be involved in fungal intraspecific communication [13], but bioactive DKPs secreted by fungi could bring false information to competitors, like gram-negative bacteria or archaea in microbial communities. Ultimately, competitors control cell densities, and thus fungi survive and grow under limited resources. 2,4-Dichlorobenzoic Acid (1). White solid. ESI-MS m/z: 188.9 [M – H]–/191.0 [M – H]–/193.3 [M – H]–, with intensities in a ratio of 9:6:1. 1H NMR (500 MHz, CDCl3, , ppm, J/Hz): 7.99 (1H, d, J = 8.5, H-6), 7.53 (1H, d, J = 2.0, H-3), 7.35 (1H, dd, J = 8.5, 2.0, H-5). 13C NMR (125 MHz, CDCl3, , ppm): 127.2 (C-1), 136.0 (C-2), 131.5 (C-3), 139.6 (C-4), 126.6 (C-5), 133.5 (C-6), 169.4 (C-7). Cyclo-(Pro-Val) (2). White solid. 1H NMR (500 MHz, CD3OD, , ppm, J/Hz): 4.22 (1H, t, J = 7.3, H-2), 4.06 (1H, m, H-4), 3.58 (1H, m, H-5a), 3.52 (1H, m, H-5b), 2.34 (1H, m, H-6a), 2.03 (1H, m, H-6b), 2.51 (1H, m, H-7a), 1.98 (1H, m, H-7b), 1.97 (1H, m, H-8), 1.12 (3H, d, J = 7.0, H-9), 0.96 (3H, d, J = 7.0, H-10). 13C NMR (125 MHz, CD3OD, , ppm): 167.6 (C-1), 60.1 (C-2), 172.6 (C-3), 61.5 (C-4), 46.2 (C-5), 23.3 (C-6), 29.5 (C-7), 29.9 (C-8), 18.8 (C-9), 16.7 (C-10).

2-Amino-3,4,5,6-tetra­fluoro­benzoic acid

The asymmetric unit of the title compound, C7H3F4NO2, obtained as an intermediate in the synthesis of a coupling reagent, contains four independent and conformationally similar molecules. The amine H atoms form both intramolecular and intermolecular N—H⋯Ocarboxyl hydrogen bonds which, together with intermolecular O—H⋯Ocarboxyl hydrogen bonds and N—H⋯F associations form ribbon structures along the a axis.

Methyl 2-amino-3,4,5,6-tetra-fluoro-benzoate.

In the title compound, C8H5F4NO2, synthesized by esterification of 2,3,4,5-tetrafluoroanthranilic acid with methanol, an intramolecular amine N—H⋯Ocarbonyl hydrogen bond is present, while intermolecular N—H⋯O hydrogen bonds produce chains in the crystal, which extend along the b-axis direction.

Aqua-(2-oxido-2,2-diphenyl-acetato-κO,O)(1,10-phenanthroline-κN,N')copper(II).

In the title mononuclear complex, [Cu(C14H10O3)(C12H8N2)(H2O)], the CuII atom is five-coordinated by two N atoms from a 1,10-phenanthroline (phen) ligand, two O atoms from a benzilate ligand and one O atom from a water molecule in a distorted square-pyramidal geometry. The crystal structure is stabilized via intermolecular O—H⋯O and C—H⋯O hydrogen bonds, C—H⋯π interactions and π–π stacking interactions between the pyridine and benzene rings of neighboring phen ligands [centroid–centroid distances = 3.684 (2), 3.564 (2) and 3.380 (1) Å].

3‐(4‐Bromo‐1H‐pyrrole‐2‐carbox­amido)­propanoic acid

# 2005 International Union of Crystallography Printed in Great Britain – all rights reserved The title compound, C8H9BrN2O3, was synthesized by condensation of -alanine methyl ester with 4-bromo-2(trichloroacetyl)pyrrole, followed by saponification and acidification. In the molecule, all bond lengths and angles are normal. The crystal packing is stabilized by intermolecular N—H O and O—H O hydrogen bonds.

N-Methyl-l-leucyl-l-leucine hydro­chloride monohydrate

In the title compound C13H27N2O3 +·Cl−·H2O, obtained by deprotecting the amino and carboxyl groups of an intermediate in the synthesis of the cyclic pentapeptide Galaxamide, a number of hydrogen-bonding interactions occur including aminium N—H⋯Cl, amide–carboxyl N—H⋯O, water O—H⋯Cl and carboxyl–water O—H⋯O associations. The aminium N—H⋯Cl⋯H—N bridging extensions give rise to zigzag chains extending along the a axis, the overall two-dimensional structure lying in the (110) plane.